1. Field of the Invention
The present invention relates to a thermal transfer recording sheet which produces glossless and matte impressions.
2. Discussion on Related Art
Recently, extensive development has been made on thermal transfer recording which forms a transferred image on a plain paper by a thermal printer or thermal facsimile. This thermal transfer recording is recently widely used because mechanism of device is simple and its maintenance is easy and besides price and maintenance cost of device are low; clear and fast recording can be performed with low energy; and color printing is relatively easy by using multi-color ink sheets. Especially, use of thermal transfer recording sheet of monochromatic type is increased owing to spread of thermal printer for word processors and thermal facsimile.
However, images recorded by thermal printer are generally high in gloss. In multi-color recording, not only definition of recording, but also aesthetic quality are required as in the fields of graphic design and full color copying and these characteristics greatly contribute to gloss of image.
On the other hand, recording of monochromatic type is mainly used in the fields of recording or copying of letters. In this case, when people read the impressed images, they feel great eye fatigue with increase of gloss of the images. This is one of the problems to be improved in thermal transfer recording. That is, glossless matte impressions are strongly demanded in thermal transfer recording of monochromatic type.
There are many known techniques of thermal transfer recording which provides glossless matte impressions.
Japanese Patent Kokai No. 60-101084 discloses a method according to which the surface to be provided with a heat-meltable ink layer of a base film is matted by sandblasting or by film molding with incorporation of fine particles.
Further, Japanese Patent Kokai No. 56-164891 discloses incorporation of a matting agent into a heat-meltable heat-sensitive ink.
Moreover, Japanese Patent Kokai No. 60-101083 discloses to provide a matting layer on a base film.
However, the methods disclosed in these patent publications suffer from various problems.
For example, the method of sandblasting the surface of a base film has the defects of reduction in strength of the film and high cost. The method of molding the film with incorporation of fine particles has the defect that degree of matting cannot be increased unless the fine particles are incorporated in a large amount.
The method of incorporating a matting agent into ink has the defects that since the matting agent is ordinarily a white inorganic pigment, matting effect is difficult to exhibit with addition of the matting agent in a small amount while addition of the matting agent in a large amount causes deterioration in quality of impressions and decrease in transfer density.
Furthermore, the method of providing a matting layer on a base film has the defects that the ink of the matting layer comprises a binder and an inorganic pigment and in order to exhibit matting effect, it is necessary to increase matting depth in the matting layer and thus it becomes necessary to increase particle size of the inorganic pigment or to use the inorganic pigment in a large amount.